猪肺炎支原体LAP激活纤溶系统诱导宿主纤毛黏液屏障破坏机制研究

对宿主纤毛黏液屏障系统的破坏是猪肺炎支原体（Mycoplasma hyopneumoniae, Mhp）感染的典型特征，诱导宿主纤溶系统的激活是该过程的关键步骤，但目前机制尚不清楚。亮氨酸氨肽酶（LAP）是Mhp新鉴定的毒力因子，申请人前期研究发现，它位于Mhp细胞表面，不仅能介导Mhp对宿主的黏附，还具备纤溶酶原结合活性，提示LAP可能在Mhp激活宿主纤溶系统诱导纤毛黏液屏障破坏这一过程发挥重要作用。本项目，一方面结合互作分析，拟通过解析LAP及其与纤溶酶原复合物的晶体结构，从原子水平揭示LAP与纤溶酶原的相互作用机制；另一方面，通过本动物试验，分别阻LAP和纤溶酶原活性，观察Mhp攻毒后对纤毛黏液屏障破坏的影响，进一步明确LAP通过激活纤溶系统诱导纤毛黏液屏障的破坏作用及机制。本项目的开展，将有助于理解LAP诱导Mhp对宿主呼吸道的入侵机制，同时也为抗支原体药物新靶标的发现提供思路。

Destruction of the host cilium-mucous barrier is a typical feature of Mycoplasma hyopneumoniae (Mhp) infection. Activation of the host fibrinolytic system is the key step in the process, but the mechanism is still unknown. Leucine aminopeptidase (LAP) is a newly identified virulence factor of Mhp. The previous study found that it was located on the surface of Mhp cells. LAP not only mediates the adhesion of Mhp to the host, but also has plasminogen-binding activity. So it is supposed that LAP may play an important role in the process of cilium-mucous barrier destruction, which is mediated by fibrinolytic system during Mhp infection. In this project, we are going to determine the crystal structures of LAP and its complex with plasminogen. It will be helpful for understanding the interaction mechanism between LAP and plasminogen. On the other hand, we are going to block the functions of LAP and plasminogen respectively during Mhp infection, and to investigate the effect of LAP and plasminogen on the disruption of cilium-mucous barrier. This will help us to understand the mechanism of cilium-mucous barrier disruption, which is mediated by fibrinolytic system and induced by Mhp LAP. This project will help to understand the mechanism that how Mhp LAP induces the invasion to the host respiratory tract. It will also give insights for the development of new anti-mycoplasma drugs.